Merge branch 'xbt_random' into 'master'

[simgrid.git] / src / xbt / random.cpp

diff --git a/src/xbt/random.cpp b/src/xbt/random.cpp
index 03c544a..63d5353 100644 (file)
--- a/src/xbt/random.cpp
+++ b/src/xbt/random.cpp
@@ -19,6 +19,9 @@ int uniform_int(int min, int max)
   unsigned long gmax   = mt19937_gen.max();
   unsigned long grange = gmax - gmin + 1;
   unsigned long range  = max - min + 1;
+  xbt_assert(
+      min < max || min == max,
+      "The maximum value for the uniform integer distribution must be greater than or equal to the minimum value");
   xbt_assert(range < grange || range == grange, "The current implementation of the uniform integer distribution does "
                                                 "not allow range to be higher than mt19937's range");
   unsigned long mult       = grange / range;
@@ -42,25 +45,25 @@ double uniform_real(double min, double max)
 
 double exponential(double lambda)
 {
-  unsigned long numerator = mt19937_gen() - mt19937_gen.min();
-  unsigned long divisor   = mt19937_gen.max() - mt19937_gen.min();
-  return -1 / lambda * log(numerator / divisor);
+  return -1 / lambda * log(uniform_real(0, 1));
 }
 
 double normal(double mean, double sd)
 {
-  unsigned long numeratorA = mt19937_gen() - mt19937_gen.min();
-  unsigned long numeratorB = mt19937_gen() - mt19937_gen.min();
-  unsigned long divisor    = mt19937_gen.max() - mt19937_gen.min();
-  double u1                = numeratorA / divisor;
+  double u1 = 0;
   while (u1 < std::numeric_limits<double>::min()) {
-    numeratorA = mt19937_gen() - mt19937_gen.min();
-    u1         = numeratorA / divisor;
+    u1 = uniform_real(0, 1);
   }
-  double z0 = sqrt(-2.0 * log(numeratorA / divisor)) * cos(2 * M_PI * numeratorB / divisor);
+  double u2 = uniform_real(0, 1);
+  double z0 = sqrt(-2.0 * log(u1)) * cos(2 * M_PI * u2);
   return z0 * sd + mean;
 }
 
+void set_mersenne_seed(int seed)
+{
+  mt19937_gen.seed(seed);
+}
+
 } // namespace random
 } // namespace xbt
 } // namespace simgrid